For some time, there has been an interest in devices and methods for quantum interference. In U.S. Pat. No. 5,157,467 in the name of Fujii two prior art quantum devices are shown in FIGS. 1 and 2 and are described with reference to these figures.
The device of FIG. 1 operates in the following fashion. An electron wave injected by an electrode 10 is propagated through a part (left end part in FIG. 1) in which the distance between two electron waveguides 11 and 12 is made short enough to couple the electron wave, and arrives at decoupling part 15 or wave branching part. In this decoupling part indicated by dotted loop lines on the left side in FIG. 1, the distance between two electron waveguides 11 and 12 is made longer than that in the coupling part at the left end part, so that the electron wave divides into two waves in this decoupling part. In the coupling part 16 Si is doped so that the Fermi level in the two electron wave waveguides 11 and 12 may be located between first and second quantum levels or subbands. Thus, the electron wave is concentrated solely into the first level below the Fermi level, leading to the coupling of the electron waves. Practically, the coupling and decoupling are achieved by varying the thickness of an ALAS layer which is a barrier layer 13. That is, the barrier 13 is thinner at the two ends so that there is considerable tunneling between the waveguides or wells 11 and 12 at the ends but hardly any tunneling in the central region.
In the decoupling part 15, the phase difference between the two electron waves is due to the AB effect (more in detail, magnetostatic AB effect) by applying thereto the magnetic field in a direction normal to the coupling part 16 on the right side in FIG. 1 indicated by dotted looplines, and thus there is generated a bonding state having a lower energy or antibinding state having a higher energy. Here the Fermi level is adjusted by doping, so that only the electron wave having lower energy reaches a drain 14. That is, an effect similar to the optical interference effect occurs between the two coupling electron waves, and there are cases where electrons can reach the electrode 14 at the detection side and where electrons do not reach the electrode. As a result, on/off control of the device is performed.
Further there has also been proposed a device such as shown in FIG. 2 of U.S. Pat. No. 5,157,467 that utilizes real space transfer without using the tunneling phenomenon. The device of FIG. 2 does not utilize the electron wave, but such a device can readily be modified to take the electron wave out the quantum structure by replacing the layer 20 through which current flows with a quantum well or the like. The idea for this device is based on the energy discontinuity at a heterojunction region.
In an attempt to overcome disadvantages with these two prior art devices, U.S. Pat. No. 5,157,467 discloses a device that overcomes the problem of reflected electron waves as well as the problem of dispersion of wave numbers in conducted electrons. Fujii's device includes a source, a drain and waveguides with quantum structures between the source and the drain. An electron wave from the source that is confined in the waveguides is split into plural electrons waves. The phase difference between the split electron waves is controlled and the split electron waves are combined into a single electron wave. The combined electron wave is directed to the drain or out of the waveguides according to an energy state of the combined electron wave by a real space transfer such as a tunneling effect. The phase difference control is achieved by varying one of an electric field, a magnetic field or light.
Although all of these prior an devices appear to perform their intended functions, some better than others, all of these devices require leads attached to them for generating electron waves. As well, all of these devices utilize physical structures within the device to direct and combine electron waves.
It is an object of this invention, to provide a method and an apparatus for generating and controlling the direction of photoelectrons by varying the phase relationship between input optical signals.
It is an object of the invention to provide an apparatus of controlling a direction of phototelectrons in a semiconductor material, wherein the semiconductor has no input leads.